Rising atmospheric carbon dioxide (CO₂) levels are a major contributor to global warming. The electrochemical reduction of CO₂ (CO₂RR) into value-added products offers a promising strategy to mitigate the CO2 levels. This process is typically performed in a CO₂ electrolyser. Advances in electrolyser configurations, including H‑cells, flow cells, and membrane electrode assemblies (MEAs) have improved efficiency and product selectivity. However, H‑cells and flow cells rely on liquid electrolytes, which face limitations such as low CO₂ solubility, electrolyte leakage, and costly product separation. MEA systems minimise ohmic losses, yet cation‑exchange‑membrane-based MEAs often promote hydrogen evolution, reducing CO₂RR selectivity. The aforementioned limitations have promoted interest in solid-state electrolysers, where the application of solid electrolytes (SEs) can facilitate controlled ion transport, reduced hydrogen evolution, and elimination of liquid‑phase challenges. Polymer-based SEs, such as sulfonated polystyrene divinylbenzene resins (e.g., Dowex), have delivered high Faradaic efficiencies and pure product streams. However, they are petroleum-derived, expensive, and not optimised for CO₂RR, highlighting the urgent need for sustainable alternatives.Cellulose, the most abundant natural polymer, has emerged as a promising SE candidate due to its low cost, renewability, and tuneable functional groups. Although native cellulose exhibits low ionic conductivity, its hydroxyl groups can be functionalised into sulfonates to enhance ion transport. Pretreatment and mechanical refining can adjust crystallinity and increase functional‑group accessibility. Furthermore, nano-structuring improves surface area and active‑site density, potentially boosting electrochemical performance.This research investigates sulfonated cellulose within CO₂ electrolyser environments, an area that remains unexplored. As the work is in its initial stages, emphasis is on establishing structure-property relationships and identifying factors relevant to future device-level integration. This study examines key physicochemical properties, including ion transport, water uptake, degree of functionalisation, and structural stability. Insights gained will support the development of sustainable cellulose-based solid electrolytes for next‑generation electrochemical technologies.